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These commercially available natches are 9 mm deep (to the shoulder) inside, the inside diameter is 9.4 mm, they are 10.9 mm high at the shoulder and 18.3 mm total height. The challenge is to embed receptables (two inside this box) into plaster case molds. The embedded natches hold natches precisely in place for the plaster pour of the working mold. How can they be embedded? A simple 9.4 mm dia hole in the 3D printed block mold (which this box simulates). How are the embeds held in place? The two cylindrical flanged retainers on the outsides fit through the holes and embeds on the inside slide snuggly over them.
Imagine the plaster fill of this box creating a case mold with embeds for foot-first and head-first natches. How are the natches held in place by the embeds? The nipple fits snuggly into one. A 9.4 mm cylinder inserts into both the embed and the natch.
Top left to right: The natch, the retainer, a fragment of a 0.8mm thick 3D printed mold shell and the shallow and deep receptacles that fit snuggly over it.
Lower left: The deep and shallow receptacles are embedded in a test section of plaster, the natches are ready to insert (head first or feet first). The natches have been glued in on the right.
Not shown: Cylindrical retainers that fit inside the embeds. These enable replication of an embed in a case mold to an embed in a working mold.
In some ways, these are preferable to the commercially available natches. First, the embeds enable flexibility in what will be inserted into either case or working molds (the natches, for example, are glued into the embeds). A key advantage of this, vs using commercial natches, is that working molds release from the case molds with flat matting surfaces - meaning they can be sanded to ultimate flatness for optimal fit (since a little warp can happen in the 3D printed block mold). Another advantage is that parametric drawings make it easy to change the sizes of all needed parts. This project is a testament to the accuracy of 3D printing - it is precise enough, on our Prusa MK4, that 1/10 mm is the difference between perfect fit and too tight or too loose.
Projects |
Mold Natches
Natches are an interlocking mechanism using in plaster molds for ceramics. They enable quick and accurate registry when assembling multiple pieces of a mold. |
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Glossary |
Mold Natches
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